I'd really appreciate a solution to this problem, too.
I work at a forum that has a problem with a certain clique of people being jackasses all the time and posting enormous pictures in reputation comments to antagonise the recipient. Since they're technically not breaking any of our written rules on the forum, they aren't getting themselves punished, but putting a nix on this would really help me out.
Case in point, the most recent image that our administrative staff have been asked to remove:
http://www.earthstation1.com/WWIIPic...rSalutesSS.jpg